This invention is directed generally to the power supply arts, and more particularly a novel ultra-wide input range switching power supply for circuit protection devices.
Power supply designs for small circuit and personnel protection devices have environmental and operating constrains not common to most xe2x80x9cconventionalxe2x80x9d line powered devices. Such a power supply should be designed such that 1) it survives and operates under the extreme line conditions typical for power systems including lightning induced surge events and wide voltage fluctuations, 2) efficiency is kept as high as possible to reduce the generation of excess heat, and 3) electronic trip drive circuitry for the circuit protection device is designed into the power supply to reduce the number of required components. The design discussed herein uses a novel approach to buck-type switching power converter that complies with susceptibility and input range requirements, minimizes power loss, and incorporates the drive circuitry for energizing a solenoid. A more detailed discussion of the problems solved follows.
Providing electronics with power throughout an extremely wide range of input voltage. A circuit performing fault detection in a circuit breaker must remain functional during the detection and tripping process. When a fault occurs, the input voltage to the power supply of a detection device may fall to low levels. The power supply must continue, under those conditions, to supply the electronics with the energy required to detect the fault and open the circuit. Previously, power supplies for circuit breakers operate under the conditions present in load centers where large conductors provide AC power. However, as the need for smart detection of arcing and other types of faults expands to include protection at the outlet or load device, voltage drop under fault conditions increases due to the added series impedance of smaller wiring. New designs will require wider input voltage operating ranges that meet these requirements.
Providing efficient power conversion. As the performance of xe2x80x9csmart circuit protectorsxe2x80x9d such as arc detection circuits increases, so does the power requirement. Space constrains and heat generated from the circuit breaker itself leave little allowance for added heat dissipation from the electronics. In particular, the power supply must be efficient enough to do the required power conversion without dissipating excess heat. Previous designs for lower power circuits use a linear approach. Excessive power is lost in these designs when they are scaled for higher output power.
Providing a method for operating an in-line solenoid for tripping operation using the power supply switching transistor. The electronics in a circuit breaker ultimately provides protection by opening a set of contacts. Energizing a solenoid that provides mechanical force to delatch the mechanism holding the contacts generally does this. In the past, energizing this solenoid required a dedicated high current device that is switched on by the protection circuit.
U.S. Pat. No. 6,121,762 discloses a power supply scheme designed to minimize power consumption in the control circuit, and to eliminate the need for the isolation block between the control circuit and the switch. The invention proposed herein obtains similar results but differs from the above patent since the need for the local supply and control isolation is eliminated by the relocation of the switching element and a novel control scheme. Additionally, the invention proposed herein allows the supply switch to be used to drive a solenoid placed in the input filter circuit.
However, with this invention, no bias supply is required since the energy used to operate the switching transistor is derived directly from the supply output itself. This results in an optimization of efficiency and a reduction of parts count when compared to previous designs that use a bias-supplied switch controlled circuit. Additionally, output regulation can be achieved over an extremely wide range of input voltages (10:1 or more).
Previous designs have achieved a range of approximately 2:1. The extra wide range capability is made possible because the only constraints on input voltage are that 1) the peak input voltage does not exceed a value that would cause a violation of component ratings, and 2) that the input voltage has an rms value that is a few volts above the regulated output voltage.
A solenoid is placed in-line with the power supply and can be driven through the power supply regulation circuitry with the addition of one small-signal transistor. Previous designs required a separate SCR or TRIAC and driving circuitry.
The elimination of the bias supply requirement and the ability to drive a solenoid with the power supply switching transistor were made possible by moving the switching element from the classic buck converter location on the high-side to the low-side. A novel combination of components was then used for the low-side switch control scheme that derives its power and voltage feedback from the supply output. The supply control circuit remains powered under solenoid trip operation due to a clamped output condition, further described below.
The invention has a number of potential applications including, but not limited to, arc fault protection circuit breakers; electronic trip units; and arc fault protected devices such as wall sockets, outlet strips, electrical appliances and the like.
Briefly, in accordance with the foregoing, a wide input range switching power supply apparatus for a circuit protection device comprises a supply input, a rectifier circuit for rectifying an AC line voltage at the supply input, and a switch-mode DC-to-DC converter coupled to the rectifier circuit for providing a low voltage DC power to a load at a supply output, the converter comprising a switch having an open state and a closed state and a control circuit for controlling the state of the switch, wherein the control circuit is operatively coupled to receive operating power from the supply output.
In accordance with another aspect of the invention, a wide input range switching power supply for a circuit protection device comprises a rectifier circuit for rectifying an AC line voltage, and a switch-mode DC-to-DC converter coupled to the rectifier circuit for providing a low voltage DC power to a load, the converter comprising a switch having an open state and a closed state and a control circuit for controlling the state of the switch, and an input filter operatively coupled with the rectifier circuit, the input filter including a solenoid coil also operative for driving a trip mechanism of the circuit protection device.
In accordance with another aspect of the invention, a circuit protection device comprises a detection device for detecting a predetermined condition in a circuit, a trip mechanism operatively coupled with said detection device for opening and closing a current path to a circuit to be protected by the circuit protection device, a solenoid coil for energizing the trip mechanism, and a wide input range switching power supply comprising a supply input, a rectifier circuit for rectifying an AC line voltage at the supply input, and a switch-mode DC-to-DC converter coupled to the rectifier circuit for providing a low voltage DC power to a supply output, the converter comprising a switch having an open state and a closed state and a control circuit for controlling the state of the switch; wherein the control circuit is operatively coupled to receive operating power from the supply output.
In accordance with another aspect of the invention, a circuit protection device comprises a detection device for detecting a predetermined condition in a circuit to be protected, a trip mechanism operatively coupled with said detection device for opening and closing a current path to a circuit to be protected by the circuit protection device, a solenoid coil for energizing the trip mechanism, and a wide input range switching power supply comprising a supply input, a rectifier circuit for rectifying an AC line voltage at the supply input, and a switch-mode DC-to-DC converter coupled to the rectifier circuit for is providing a low voltage DC power at a supply output, the converter comprising a switch having an open state and a closed state and a control circuit for controlling the state of the switch, and an input filter operatively coupled with the rectifier circuit, the input filter including the solenoid coil.
In accordance with another aspect of the invention, a method for supplying power to a circuit protection device over a wide input range comprises rectifying an AC line voltage at a supply input, providing a low voltage DC power to a load using a switchmode DC-to-DC converter, including a switch having an open state and a closed state and a control circuit for controlling the state of the switch, and filtering the rectified AC line voltage using a filter including a solenoid coil also operative for driving a trip mechanism of the circuit protection device.
In accordance with another aspect of the invention, a wide input range switching power supply apparatus for a circuit protection device comprises a supply input, means for rectifying an AC line voltage at the supply input, and converter means coupled to the means for rectifying for providing a low voltage DC power to a supply output, the converter means comprising switch means having an open state and a closed state and a control circuit for controlling the state of the switch means, wherein the control circuit means is operatively coupled to receive operating power from the supply output.
In accordance with another aspect of the invention, a wide input range switching power supply for a circuit protection device comprises means for rectifying an AC line voltage, converter means coupled to the means for rectifying for providing a low voltage DC power to a supply output, the converter means comprising switch means having an open state and a closed state and control circuit means for controlling the state of the switch means, and means for filtering the rectified AC line voltage including a solenoid coil also operative for driving a trip mechanism of the circuit protection device.
In accordance with another aspect of the invention, a circuit protection device comprises trip means for opening and closing a current path to a circuit to be protected by the circuit protection device, a solenoid coil for energizing the trip means, and a wide input range switching power supply apparatus comprising a supply input, means for rectifying an AC line voltage at the supply input and converter means for providing a low voltage DC power to a supply output, the converter means comprising switch means having an open state and a closed state and control circuit means for controlling the state of the switch means, wherein the control circuit means is operatively coupled to receive operating power from the supply output.
In accordance with another aspect of the invention, a method for supplying power to a circuit protection device over a wide input range comprises rectifying an AC line voltage at a supply input, providing a low voltage DC power to a supply output using a switch-mode DC-to-DC converter including a switch having an open state and a closed state and a control circuit for controlling the state of the switch, and operatively coupling the control circuit for receiving operating power from the supply output.
In accordance with another aspect of the invention, a circuit protection device comprises a trip means for opening and closing a current path to a circuit to be protected by the circuit protection device, a solenoid coil for energizing the trip means, and a wide input range switching power supply comprising means for rectifying an AC line voltage, converter means coupled to the means for rectifying for providing a low voltage DC power to a supply output, the converter means comprising switch means having an open state and a closed state and control circuit means for controlling the state of the switch means, and means for filtering the rectified AC line voltage including said solenoid coil.